The Stack was introduced in the 6th edition rules change (1999) and still works the same way today. The 6th edition rules also unified the instant and interrupt types, because the separate interrupt type was only necessary in the old "batch-based" system.

The modern stack is so much more sane than the old batch based system. You can still do plenty of interesting things with it, like casting Blessed Alliance during the end of combat step to get rid of Giest of Saint Traft, or casting Infernal Tutor, then holding priority and cracking a Lion's Eye Diamond, or responding to an O-ring trigger with another O-ring for a permanent exile, or burning somebody out in responding to a lethal mana-barbs trigger.